When to use Sub-domains versus Sub-directories and Microsites

Thursday, 17th June 2010 by Simon. Average Reading Time: about 3 minutes.

When should I use sub-domains versus sub-directories? How do microsites fit into the mix?

The decision on whether to a sub-domain (e.g., xyz.domain.com), sub-directory (e.g., www.domain.com/xyz) or even a microsite is may simply be a decision based on your website’s architecture, but it is often compounded by a decision made within the marketing team. In general, sub-directories are used to describe what individual pages are about while sub-domains and microsites are used to describe what an entire site is about.

When to use sub-directories

Sub-directories are useful for organising content into meaningful groupings with descriptive URLs. If you have a meaningful taxonomy, then sub-directories are a good way to make your URLs more search friendly.

For relatively small websites, i.e. not the BBCs and CNNs of this world, keeping your content in one place will help your website build trust and authority. The more trust and authority a website is able to garner with the search engines, the easier it becomes to rank new and related content.

For the less technically savvy, sub-directories are easier to manage than sub-domains since they are generally created as part of the website’s page hierarchy. Furthermore, many CMSs don’t support the ability to publish across different domains out-of-the-box.

Google Webmasters tools allow you to set basic geo-location preferences to sub-directories. The idea is to create new pseudo-website listings that also include sub-directories. For example, the www.domain.com listing could have www.domain.com/uk for the UK, www.domain.com/es for Spain and so on for each geographic location.

When to use sub-domains

Sub-domains are useful for organising content that is otherwise unrelated. Take Google for example, they have a news product at news.google.com, a maps product at maps.google.com and a email product at mail.google.com. Since they are fundamentally different from each other and Google’s main search product, they aren’t held under the same domain.

Sub-domains allow you to target regional markets more effectively. Sub-domains are easier to market to specific geographical regions. For instance you can assign an IP address to a sub-domain and set a geographical preference in Google’s Webmaster tools for each sub-domain (sub-directories can have their geo-preference set but can’t be assigned an IP in another country, which might also be a signal of geo-location). For example, the www.domain.com listing could have uk.domain.com for the UK, es.domain.com for Spain and so on for each geographic location.

If you already have a well established domain and want to expand out into other areas not completely related to your main website’s activities then a sub-domain may well be a good option. At the same time, people associate the sub-domain with your main domain’s brand, which means it can be easy to build up momentum on a vertical related to your main site. This is what the web giants Google and Yahoo, Sky and the BBC do successfully, but smaller websites can do the same. You often see this when the third-party functionality is “plugged into” an existing site, such as a payment gateway, events and job boards.

When to use microsites

Like sub-domains, microsites have an important position in the overall debate.

If you have a new product or service that you potentially want to sell off or brand completely differently from your main business offering, a microsite makes a lot of sense. Microsites are really just a stripped down website, but as the product or service develops, so will the website and associated brand and it will take on trust and authority of its own.

Microsites offer the ability to completely separate your main brand from the new product, service or promotion. This is useful if you’re pushing a content piece that has little to no association with your site and you don’t want the potential branding confusion or commercial association to hinder link and user growth.

Microsites can be powerful if you have an exact match domain name for a particular keyword you’re targeting. Google’s preference for and ranking exact-match domains is a very powerful tool to use for SEO.

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